System and method for determining placement of a tracheal tube

ABSTRACT

According to various embodiments, a tracheal tube may employ optical sensing techniques for determining a distance between the inserted tube and an anatomical structure such as a carina. The distance information may provide an indication as to whether or not the tracheal tube is properly placed within the trachea. The optical techniques may include interferometry.

BACKGROUND

The present disclosure relates generally to medical devices and, moreparticularly, to airway devices, such as tracheal tubes.

This section is intended to introduce the reader to aspects of the artthat may be related to various aspects of the present disclosure, whichare described and/or claimed below. This discussion is believed to behelpful in providing the reader with background information tofacilitate a better understanding of the various aspects of the presentdisclosure. Accordingly, it should be understood that these statementsare to be read in this light) and not as admissions of prior art.

In the course of treating a patient, a tube or other medical device maybe used to control the flow of air, food, fluids, or other substancesinto the patient. For example, tracheal tubes may be used to control theflow of air or other gases through a patient's trachea. Such trachealtubes may include endotracheal (ET) tubes, tracheotomy tubes, ortranstracheal tubes. In many instances, it is desirable to provide aseal between the outside of the tube or device and the interior of thepassage in which the tube or device is inserted. In this way, substancescan only flow through the passage via the tube or other medical device,allowing a medical practitioner to maintain control over the type andamount of substances flowing into and out of the patient.

For example, a patient may be intubated when an endotracheal tube isinserted through the patient's mouth and into the trachea. Often, suchintubation procedures may be performed during medical emergencies orduring critical care situations. As such, healthcare providers maybalance a desire for speed of intubation with a desire for accurateplacement of the tube within the trachea. However, proper placement of atracheal tube may be complex. In certain situations, placement may beaided with visualization of the trachea performed during laryngoscopy.During an intubation procedure, a practitioner may employ a lightedlaryngoscope during introduction of the endotracheal tube. However,often the visualization of the trachea is poor because of patientsecretions that may obscure the laryngoscope. In addition, suchvisualization during introduction of the tube may not account forongoing changes in the tube's position within the trachea that may occurwhen a patient coughs, which may dislodge a tube from its desiredlocation, or when a patient is jostled or moved within a care setting,which may change the position or angle of the tube within the trachea.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the disclosure may become apparent upon reading thefollowing detailed description and upon reference to the drawings inwhich:

FIG. 1 illustrates an exemplary system including an endotracheal tubewith a coherent light source and detector according to embodiments;

FIG. 2 is a schematic diagram of an interferometer that may be coupledto a tracheal tube according to embodiments;

FIG. 3 is a flow diagram of a method of operating a tracheal tubeaccording to embodiments;

FIG. 4 is a perspective view of an exemplary endotracheal tube of FIG.3; and

FIG. 5 is a perspective view of an exemplary distal tip of a trachealtube with embedded optical fibers that may be coupled to a coherentlight source and photodetector.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

One or more specific embodiments of the present disclosure will bedescribed below. In an effort to provide a concise description of theseembodiments, not all features of an actual implementation are describedin the specification. It should be appreciated that in the developmentof any such actual implementation, as in any engineering or designproject, numerous implementation-specific decisions must be made toachieve the developers' specific goals, such as compliance withsystem-elated and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

A tracheal tube may be used to seal a patient's airway and providepositive pressure to the lungs when properly inserted into a patient'strachea. Positioning the tracheal tube at a desired position within thetrachea, for example during endotracheal intubation, may improve theperformance of the tracheal tube and reduce clinical complications. Inparticular, the distal inserted end of the endotracheal tube may bepositioned in the patient's trachea at a location substantially betweenthe patients vocal cords and carina. If the tube cuff is not insertedfar enough past the vocal cords, for example, the tube may become moreeasily dislodged. If the tube is inserted too far into the trachea, suchas past the carina, then the tube may only function to adequatelyventilate one of the lungs, rather than both. Thus, proper placement ofthe distal tip of the tube may result in improved ventilation to thepatient.

Provided herein are tracheal tubes and systems for facilitating properplacement of the tracheal tube relative to certain anatomical structuresin and around the patient's airway and trachea. Such tracheal tubes mayinclude assemblies for shining coherent light into the trachea anddetecting the returned light. The light is returned after beingreflected/scattered by internal tissues of the patient (such as thetissues in the vicinity of the carina). Accordingly, information relatedto the detected light, for example its phase relative to a reference,may be used to determine a distance from the tube to the anatomicalstructure in question. In embodiments, a distance from the distal end ofthe tracheal tube to the carina (or other internal anatomical structureor tissue) may be determined. A healthcare provider may then use theinformation about the location of the tracheal tube relative to theanatomical structures (e.g., the carina) to determine whether the tubeis properly placed or whether the position of the tube should beadjusted.

In embodiments, the disclosed tracheal tubes, systems, and methods maybe used in conjunction with any appropriate medical device, includingwithout limitation a feeding tube, an endotracheal tube, a tracheotomytube, a circuit, an airway accessory, a connector, an adapter, a filter,a humidifier, a nebulizer, nasal cannula, or a supraglottic mask/tube.The present techniques may also be used to monitor any patientbenefiting from mechanical ventilation, e.g., positive pressureventilation. Further, the devices and techniques provided herein may beused to monitor a human patient, such as a trauma victim, an intubatedpatient, a patient with a tracheotomy, an anesthetized patient, acardiac arrest victim, a patient suffering from airway obstruction, or apatient suffering from respiratory failure.

FIG. 1 shows an exemplary tracheal tube system 10 that has been insertedinto a patient's trachea. The system 10 includes a tracheal tube 12,shown here as endotracheal tube) with an inflatable balloon cuff 14 thatmay be inflated to form a seal against tracheal walls 16. The trachealtube 12 may also include one or more optical source fibers 18 andoptical detection fibers 20 that are associated with the tube 12. Whenventilation is provided via the tube system, a ventilator 22 istypically provided, as discussed below. The optical source fiber 18 maybe configured to pass light from a source 24 through a distal end 27 ofthe endotracheal tube and into a patient's trachea such that a portionof the emitted light may interact with a carina 28. The emitted lightmay be transferred back through the optical detection fiber 20, whichmay be coupled to a light detector 26.

When the system 10 includes devices that facilitate positive pressureventilation of a patient, such as ventilator 22, any ventilator may beused, such as those available from Nellcor Puritan Bennett LLC. Thesystem may also include a monitor 30 that may be configured to implementembodiments of the present disclosure. The monitor 30 may be astand-alone device or may be coupled to another patient monitor or tothe ventilator 22. The monitor 30 may include a microprocessor 32coupled to an internal bus 34 and a display 36. Regardless of where itis placed, the microprocessor, or any other suitable processingcircuitry, aids in computing the distance of the distal end 27 of thetube from reference structures within the patient, such as the carina28.

The monitor 30 may include certain elements for controlling the lightsource 24 and the light detector 26. The monitor 30 may drive light fromsource 24, which in turn may be carried by optical source fiber 18. Thelight may pass into the tissue, where it may be variously scattered,absorbed, and/or reflected and then detected by detector 26. A timeprocessing unit (TPU) 38 may provide timing control signals to lightdrive circuitry 40, which controls when the light source 24 isactivated) and if multiple light sources 24 are used, the multiplexedtiming for the different light sources. TPU 38 may also control thegating-in of signals from detector 26.

The monitor 30 may be configured to receive signals from the detector 26and store the signals in a mass storage device 42, such as a RAM, ROM,optical storage device, flash memory device, hardware storage device, amagnetic storage device, or any other suitable device permitting memorystorage. The signals may be accessed and operated according toinstructions (which may also be stored in the memory circuitry) executedby the microprocessor 32. In certain embodiments, the signals may berelated to a placement of the tracheal tube 12 within the patient'strachea and may be processed by the monitor 30 to indicate whether thetracheal tube 12 is properly placed. The monitor 30 may be configured toprovide an indication about the placement of the tracheal tube 12 withinthe patient's trachea, such as an audio alarm, visual alarm or a displaymessage if the tracheal tube 12 is too far or too close to certainanatomical structures, such as the carina 28, or outside of apredetermined placement range. In an embodiment, based at least in partupon the received signals corresponding to the light received throughoptical detection fiber 20, microprocessor 32 may calculate a placementparameter of the endotracheal tube 12 using various algorithms. Theplacement parameter may relate to, measure, or provide an indication ofa distance 44 between the distal end 27 of the tube 12 and the carina 28or other anatomical structure.

FIG. 2 is a schematic representation of an exemplary interferometryarrangement that may be incorporated into system 10 for analyzingplacement of a tracheal tube 12 within a patient's trachea. In general,a reference beam may be combined with a sample beam to generateinterference peaks, corresponding to the measured distance. In thedepicted arrangement, a beam splitter 46 divides light from light source24 between a reference beam 50 and the sample beam 52. The referencebeam is configured to impinge a reflective surface 54 (e.g., a mirror),which is a distance Lm from the detector 26. In one embodiment, the beamsplitter 46 may be configured to emit the reference beam 50 towards thereflective surface 54, for example along an axis 58 in a directionsubstantially orthogonal to the sample beam 52. In such an embodiment,the placement of the reflective surface 54 may also be generallyorthogonal to the axis 62 of the sample beam 52. The distance Lm maychange as the reflective surface 54 is moved toward or away from thedetector 26. The reflective surface 54 may be under the control of areference beam controller 60 that may control the movement of reflectivesurface 54 and may be in communication with monitor 30, which includeslight drive circuitry 32 for driving light source 24. The reference beamcontroller 60 may provide information to the monitor 30 about changes inthe distance Lm. It should be understood that the depicted arrangementis merely an example of a particular low-coherence interferometryarrangement and other suitable arrangements may be employed. Forexample, in certain embodiments, a 2×2 fiber coupler may be used inplace of a beam splitter 46. For the fiber coupler case, the beams mayrun along any axis since fibers may be flexible. Accordingly, orthogonalrelationships between reference and sample arms may not hold. However,light emitted from a fiber may be normal to the reflective surface 54 inorder to have the reflected light coupled back into the fiber.

The light that is reflected from the reflective surface 54 may impinge adetector 26 to generate the reference signal, while the light that isreturned through optical detection fiber 20 may impinge a detector 26 togenerate the sample signal. In one embodiment, the sample signal and thereference beam signal are both generated at a single detector 26. In oneembodiment, TPU 38 may control gating-in of the reference beam signaland the sample signal. Both signals are combined and directed to thedetector 26, which will typically include one or more photodetectors(e.g., photodiodes) that generate measurement signals based upon thereceived radiation. The reference signal and sample signal may beanalyzed by the microprocessor 32 (e.g, via the measurement signal fromthe detector). In one embodiment, the signals may be combined to form aninterferogram. At the point of maximum interference between thereference signal and the sample signal, it may be determined that thedistance Lm is substantially equal to a distance Lc, which may bedefined as a distance between an end of the tube and the carina 28.Because Lm is known, Lc may be determined, as discussed in more detailbelow.

The light source 24 and a detector 26 may be of any suitable type. Forexample, the light source 24 may be one or more light emitting diodesadapted to transmit one or more wavelengths of light, for example in thered to infrared range, and the detector 26 may be one or morephotodetectors selected to receive light in the range or ranges emittedfrom the light source 24. A light source 24 may be a coherent lightsource, such as a laser diode or a vertical cavity surface emittinglaser (VCSEL). The light source 24 may include a broadband or “whitelight” source, in which case the detector could include any of a varietyof elements for selecting specific wavelengths, such as reflective orrefractive elements or interferometers. These kinds of emitters and/ordetectors would typically be coupled to the rigid or rigidified sensorvia fiber optics. It should be understood that, as used herein, the term“light” may refer to one or more of ultrasound, radio, microwave,millimeter wave, infrared, visible, ultraviolet, gamma ray or X-rayelectromagnetic radiation, and may also include any wavelength withinthe radio, microwave, infrared, visible, ultraviolet, or X-ray spectra.In one example of a low-coherence interferometry arrangement, the lightsource 24 may include a low-coherence laser source such as a Nd:YVO₄pumped titanium: sapphire laser that yields radiation having awavelength range from approximately 650 nm to approximately 900 nm afterpassing through a fiber.

FIG. 3 is a process flow diagram illustrating a method in accordancewith some embodiments. The method is generally indicated by referencenumber 64 and includes various steps or actions represented by blocks.It should be noted that the method 64 may be performed as an automatedprocedure by a system, such as system 10. Further, certain steps orportions of the method may be performed by separate devices. Forexample, a first portion of the method 64 may be performed by a lightsource 24 and light detector 26, while a second portion of the method 64may be performed by a monitor 30. In embodiments, the method 64 may beperformed continuously or intermittently for long-term patientmonitoring or at any appropriate interval depending on the particularsituation of the intubated patient. Further, the steps of method 64 maybe performed during insertion of the tracheal tube 12 into the patient.

According to an embodiment, the method 64 begins with emitting light,such as coherent light, at step 66 from a light source 24 coupled to oneor more optical fibers 18. The emitted light is split at step 68 into areference light beam 50 and a sample beam 52. The sample beam istransmitted through fiber 18, which is associated with tube 12 that isinserted into a patient's airway. The sample beam 52 may exit the distalend 27 of the tube 12 before interacting with anatomical structures inthe patient. Any light that is returned through detection fiber 20 andreceived by the detector 26 at step 70 may carry information about therelative position of the tube 12 and the anatomical structure that iscarried in the sample signal, generated at step 72. At step 74, thereference beam 50 is detected by the detector 26 to generate thereference signal at step 76. In an alternative arrangement, referencelight beam 50 and the sample beam 52 may be combined at the detector 26to yield interference peaks (e.g., an interferogram). Accordingly, incertain arrangements, steps 72 and 76 may be at least partiallycombined.

A monitor 30 may perform analysis of the sample signal and the referencesignal at step 78. In embodiments, the monitor may amplify and/or filterone or both of the sample signal and the reference signal prior to theanalysis, as well as the measurement signal generated by combining thetwo. In one embodiment, an interferogram may be generated by the monitor30. The interferogram may be used to determine the point of maximuminterference between the sample signal and the reference signal.Generally, this point may correspond to a point where a distance betweenan emitter 24 and the carina 28, Lc, is substantially equal to adistance between a reflective surface 54 and a detector 26, Lm. However,certain arrangements using beamsplitters, fiber couplers, or opticalfibers may influence the determinations of Lm or Lc. In certainimplementations, once the light is split by the beam splitter 46 or afiber coupler, Lm is the distance between the beam splitting point andthe reflective surface 54, while Lc is the distance from the carina 28to the same beam splitting point. It should also be understood that,because the emitter 24 and detector 26 may be coupled to optical fibersthat may not substantially alter the intensity of light as a function oftheir length, in embodiments, determining the distance 44 from Lc mayinvolve subtracting a length of the optical fiber. That is, the measuredlength or distance can be easily converted to a distance 44 between theend of the tube and the anatomical structure of interest by subtractingthe light transmission length represented by the optical fibers, anyconnectors, and so forth.

A monitor 30 may use the distance Lc as a placement parameter at step 80to determine whether this distance is acceptable by reference to adesirable placement of the tracheal tube 12. Example of placementparameters may include a calculated distance between a tube 12 and ananatomical structure. In one embodiment, a placement parameter may be aratio of a calculated distance 44 determined from Lc and an empiricallyderived or clinically measured distance associated with proper tubeplacement. For example, proper tube placement may involve a measureddistance 44 of 1-5 cm. It should be appreciated that there may beseveral empirically derived target distances, depending on the size,age, or sex of the patient. A target distance to which the measureddistance 44 may be compared may differ for adult men, who may have, inan embodiment, a predetermined target of 3-4 cm, and adult women, forwhom the predetermined target may be 2-3 cm. In other embodiments, thealarm may be triggered if the measured distance 44 is less than 3 cm,less than 2 cm, or less than 1 cm.

A placement parameter may also be an average or mean of multiple datapoints or measurements. A placement parameter may also include agraphical, visual, or audio representation of the tube/anatomicalstructure distance. For example, a placement parameter associated withproper placement may include green light indicated on a display or ashort tone generated by a speaker associated with monitor 30. Similarly,a placement parameter associated with improper placement of the tube 12may trigger an alarm at step 82, which may include one or more of anaudio or visual alarm indication. In one embodiment, the alarm may betriggered if the placement parameter is, substantially less than orsubstantially greater than a predetermined value, or outside of apredetermined range.

In one embodiment, the controller 60 may collect interferometry data atmultiple reflective surface 54 positions and the data may form multiplereference signals. That is, the distance Lm traveled by the referencebeam may be varied and matched to the distance Lc to the anatomicalfeature such that the two remain matched during intubation, providing asubstantially continuous measurement of the distance of interest. Suchmeasurements may include closed-loop control of the length of thereference length Lm by appropriate control. For example, such anembodiment may be employed for determining a placement parameter duringintubation. As the tube 12 is inserted into the patient, the reflectivesurface 54 may be moved until the distance Lc is equal to the distanceLm. For low coherence interferometric measurement, the reflectivesurface 54 may be continuously scanned back and forth. The interferencepeaks will move, corresponding to the distance Lc changes. Forapplications involving real time analysis during intubation, spectraldetection with a CCD detector array or accelerated digitization andprocessing using a field-programmable gate array (FPGA) may be used.

FIG. 4 is a perspective view of an exemplary tracheal tube 12 accordingto certain embodiments. As shown, the tube 12 may include a cuff 14 thatmay be inflated via inflation lumen 84. The tracheal tube 12 may alsoinclude a suction lumen 86 for aspirating secretions that may form abovethe cuff 14. The tracheal tube 12 may also include a plurality of fiberbundles 88. In certain embodiments, individual fibers rather than fiberbundles 88 may be used. Each fiber bundle may include one or moreoptical source fibers 18 and optical detection fibers 20. In certainembodiments, the transmitting and detecting may also take place within asingle fiber. As shown, the fiber bundles 88 may extend through thewalls 90 of the tracheal tube 12 such that they are substantially inline with a flow path 92 of the tracheal tube 12. The fiber bundles 88may include any appropriate optical connector 94 for connecting thefiber bundles 88 to components of the system 10, such as the beamsplitter 46 or the light source 24 or light detector 26.

The tube 12 and the cuff 14 may be formed from materials having suitablemechanical properties (such as puncture resistance, pin hole resistance,tensile strength), chemical properties (such as biocompatibility). Inone embodiment, the walls of the cuff 14 are made of a polyurethanehaving suitable mechanical and chemical properties. An example of asuitable polyurethane is Dow Pellethane® 2363-80A. In anotherembodiment, the walls of the cuff 14 are made of a suitable polyvinylchloride (PVC). In one embodiment, the cuff 14 may be generally sizedand shaped as a high volume, low pressure cuff that may be designed tobe inflated to pressures between about 15 cm H₂O and 30 cm H₂O. Thesystem 10 may also include a respiratory circuit (not shown) connectedto the endotracheal tube 12 that allows one-way flow of expired gasesaway from the patient and one-way flow of inspired gases towards thepatient. The respiratory circuit, including the tube 12, may includestandard medical tubing made from suitable materials such aspolyurethane, polyvinyl chloride (PVC), polyethylene teraphthalate(PETP), low-density polyethylene (LDPE), polypropylene, silicone,neoprene, polytetrafluoroethylene (PTFE), or polyisoprene.

FIG. 5 is a side view of the distal end 27 of the tracheal tube 12. Asshown, the fiber bundles 88 may extend through the walls 90 of thetracheal tube. In certain embodiments, the fiber bundles 88 may beembedded or coextruded within an extruded tracheal tube 12. When thetube 12 is manufactured, the distal end 27 may be cut on a slant tofacilitate insertion of the tube 12 in the trachea. After the tube iscut, the fiber bundles 88 may be terminated by any suitable technique.

The fiber bundles 88, or in certain embodiments, individual fibersrather than fiber bundles 88, may be distributed around thecircumference 96 of the tube wall 90. In an embodiment, three opticalbundles may be substantially evenly spaced about the circumference 96.As shown, the positioning of the fiber bundles 88 or single fibers mayinfluence the path of the light from the distal end 27 of the tube 12 tothe anatomical structure. Arrows 98, 100, and 102 illustrate threedifferent light paths from bundles 88 a, 88 b, and 88 c, respectively,to anatomical structures at or proximate to the carina 28. Arrow 98 hasa somewhat shorter path than arrow 100, which is related to its positionaround the circumference 96 relative to the carina 28, as well asdifferences in the topography of the carina 28. In addition, slightchanges in the angle within the trachea of the distal end 27 of the tube12 may influence the path of light to and from the fiber bundles 88. Incertain embodiments, light detected from all three fiber bundles 88 maybe combined or averaged to generate the data used to determine aplacement parameter. In addition, the differences in path length betweenmultiple bundles may be used to determine a placement parameter that isindicative of the orientation of the distal end 27 within the trachea.Changes in this orientation (e.g., angular displacement) may indicate ashift in tube placement that may influence cuff pressure and sealing.

In certain embodiments, the fibers or fiber bundles 88 may be formedfrom materials such as quartz, glass, or a transparent plastic, such aspoly(methyl methacrylate) or polystyrene with a fluoropolymer cladding.Examples of optical fibers include single-mode fibers, multi-modefibers, photonic-crystal fibers, hollow-core fibers,polarization-maintaining fibers and dual-clad fibers. Typical diametersfor optical fibers are from 5 to 1,000 micrometers. The optical fibermay be a single-mode fiber or a multi-mode fiber.

While the disclosure may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the embodiments provided hereinare not intended to be limited to the particular forms disclosed.Indeed, the disclosed embodiments may not only be applied tomeasurements of tracheal tube placement relative to anatomicalstructures in the trachea, but these techniques may also be utilized forthe measurement and/or analysis of the placement of other suitablemedical devices relative to other anatomical structures. For example,the present techniques may be utilized for the measurement and/oranalysis of tracheal tubes relative to tracheal walls or the vocalcords. In addition, the present techniques may be employed indetermining appropriate placement of any medical device, such as astent, catheter, implant, feeding tube, cardiac device, drug deliverydevice, or pump. Rather, the various embodiments may cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the disclosure as defined by the following appended claims.

What is claimed is:
 1. A method for determining placement of a trachealtube in a subject comprising the steps of: emitting coherent light froma plurality of optical conductors circumferentially spaced about abeveled distal end of a tracheal tube disposed in a subject, wherein thebeveled distal end is slanted relative to a wall of the tracheal tube;receiving returned coherent light after interaction with an anatomicalstructure within the subject; combining the returned coherent light witha reference beam; and determining an orientation of the tracheal tubebased upon interference between the returned coherent light and thereference beam for each of the plurality of optical conductors and adifference in path length between the plurality of optical conductors,wherein the difference in path length is representative of a position ofeach respective optical conductor about the beveled distal end.
 2. Themethod of claim 1, comprising splitting the reference beam from acoherent light source that generates the coherent light emitted fromeach respective optical conductor.
 3. The method of claim 1, wherein thereference beam is emitted in a direction substantially orthogonal to thecoherent light from each of the plurality of optical conductors.
 4. Themethod of claim 1, wherein a distance between a distal end of each ofthe plurality of optical conductors and the anatomical structure isdetermined by altering a distance traveled by the reference beam betweena moving reflective surface and a photodetector, and determining thedistance traveled.
 5. The method of claim 1, wherein determining theorientation includes determining a distance between the tracheal tubeand a carina of the subject.
 6. The method of claim 5, comprisingtriggering an alarm when the distance between the tracheal tube and thecarina is less than a first predetermined distance or greater than asecond predetermined distance.
 7. The method of claim 1, wherein thesteps are performed during intubation of the subject.
 8. The method ofclaim 1, wherein the steps are performed after intubation of thesubject.
 9. A method for determining placement of a tracheal tube in asubject comprising: using a processor to determine a distance between atracheal tube and an anatomical structure within a subject and anorientation of the tracheal tube within the subject based uponinterference between coherent light emitted from a plurality of opticalconductors circumferentially spaced about a beveled distal end of thetracheal tube and a reference beam and a difference in path lengthbetween the plurality of optical conductors, wherein the difference inpath length is representative of a position of each respective opticalconductor about the beveled distal end.
 10. The method of claim 9,comprising determining distances between a plurality of points on thebeveled distal end of the tracheal tube and one or more anatomicalstructures within the subject based upon interference between coherentlight emitted from the respective plurality of optical conductors andthe reference beam.
 11. The method of claim 9, comprising splitting thereference beam from a coherent light source that generates the coherentlight emitted from each respective optical conductor.
 12. The method ofclaim 9, wherein the distance is determined by altering a distancetraveled by the reference beam between a moving reflective surface and aphotodetector, and determining the distance traveled.
 13. The method ofclaim 9, wherein the anatomical structure comprises a carina.
 14. Themethod of claim 9, wherein the distance is determined during intubationof the subject.
 15. The method of claim 9, wherein the distance isdetermined after intubation of the subject.
 16. A system for determiningplacement of a tracheal tube in a subject comprising: a tracheal tubecomprising a plurality of optical conductors circumferentially spacedabout a beveled distal end, wherein the beveled distal end of thetracheal tube is slanted relative to a wall of the tracheal tube; aninterferometer configured to direct coherent light through the pluralityof optical conductors, to receive returned coherent light afterinteraction with an anatomical structure within the subject, and tocombine the returned coherent light with a reference beam for each ofthe plurality of optical conductors; and a processor configured todetermine an orientation of the tracheal tube based upon a signal fromthe interferometer and a difference in path length between the pluralityof optical conductors, wherein the difference in path length isrepresentative of a position of each respective optical conductor aboutthe beveled distal end.
 17. The system of claim 16, wherein theinterferometer includes a beam splitter or coupler for splitting thereference beam from the coherent light.
 18. The system of claim 16,comprising means for altering a distance traveled by the reference beam,and means for determining the distance traveled, and wherein theprocessor is configured to determine a placement parameter based uponthe distance traveled.
 19. The system of claim 18, wherein theinterferometer includes an optical detector, and wherein the placementparameter is determined as a function of a signal intensity from theoptical detector.
 20. The system of claim 18, comprising an alarmconfigured to be triggered when the placement parameter indicates thatthe tracheal tube is at a predetermined distance from the anatomicalstructure.